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If building a liquid propellant rocket engine, with bi propellants, how does the dimensions of my Combustion chamber, affect the efficiency ?

but also what is the best C* dimensions for an earth sea level engine ?

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    $\begingroup$ It will be better if you explain what C* is, many readers (including me) will not know, and include links or cited sources to what you've studied so far. Also, what exactly does "efficiency" mean? $\endgroup$
    – uhoh
    Jun 16, 2021 at 13:39
  • $\begingroup$ Remember your previous question? This is what it looked like originally and it was closed. But after it was edited, it explained in more detail and "evidence of prior research" was added, it was reopened and answered. It looks much better now! $\endgroup$
    – uhoh
    Jun 16, 2021 at 13:42
  • $\begingroup$ I don't know about the combustion chamber dimensions, but I would think that the throat diameter and the nozzle contour would have more effect on the C*. The combustion chamber just needs to provide enough volume to allow the propellant to mix and combust without exploding and introducing combustion instability. $\endgroup$
    – AJN
    Jun 16, 2021 at 14:14
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    $\begingroup$ @AJN C* is specifically defined to be independent of the nozzle, actually...depends only on the chamber pressure, throat area, and mass flow rate. And so the question doesn't make sense...at least at the level of detail that C* is used at, the combustion chamber dimensions are irrelevant. $\endgroup$
    – Christopher James Huff
    Jun 16, 2021 at 16:07

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Think of it in terms of providing enough residence time for the propellants to vaporize, mix, and burn to completion. Since most of the flow is axial, the length of the chamber contributes more directly than any other dimension to the amount of time the propellants have to burn. The second most important dimension is the throat diameter which will set your pressure, thus the density of your chamber gasses and therefore influence the speed at which the gasses traverse the length of your chamber.

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  • $\begingroup$ got it thank man $\endgroup$
    – Achillebckr
    Jun 17, 2021 at 13:30

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